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|
i386: 0.994
TCG: 0.991
kernel: 0.971
x86: 0.971
debug: 0.967
graphic: 0.962
files: 0.958
architecture: 0.951
peripherals: 0.915
device: 0.887
performance: 0.886
PID: 0.862
user-level: 0.801
socket: 0.749
semantic: 0.730
network: 0.703
KVM: 0.701
hypervisor: 0.692
assembly: 0.676
ppc: 0.630
register: 0.612
mistranslation: 0.611
vnc: 0.592
permissions: 0.586
risc-v: 0.573
VMM: 0.565
boot: 0.508
arm: 0.465
virtual: 0.355
Extra SIGTRAP when breakpoint + watchpoint occur on same instruction
Description of problem:
If a breakpoint and watchpoint occur on the same instruction in TCG, gdb receives a breakpoint notification, a watchpoint notification, and then a SIGTRAP not corresponding to any set breakpoint/watchpoint.
Steps to reproduce:
Start QEMU via:
```
./qemu-system-i386 -display none -accel tcg -kernel kernel.elf -s -S
```
Here's the gdb session:
```
(gdb) file kernel.elf
Reading symbols from kernel.elf...done.
(gdb) tar rem :1234
Remote debugging using :1234
0x0000fff0 in ?? ()
(gdb) b _start
Breakpoint 1 at 0x10000c: file kernel.s, line 17.
(gdb) c
Continuing.
Breakpoint 1, _start () at kernel.s:17
17 mov eax, 3
(gdb) b bp
Breakpoint 2 at 0x100011: file kernel.s, line 20.
(gdb) watch *(int*)&value
Hardware watchpoint 3: *(int*)&value
(gdb) c
Continuing.
Breakpoint 2, bp () at kernel.s:20
20 mov dword ptr value, eax
(gdb) c
Continuing.
Hardware watchpoint 3: *(int*)&value
Old value = 0
New value = 3
done () at kernel.s:23
23 jmp done
(gdb) c
Continuing.
Program received signal SIGTRAP, Trace/breakpoint trap.
done () at kernel.s:23
23 jmp done
```
Additional information:
This patch fixes it by disabling the extra debug interrupt if the CPU is already singlestepping, but I'm not certain it's the 'correct' fix?
```patch
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -894,7 +894,9 @@ void cpu_check_watchpoint(CPUState *cpu, vaddr addr, vaddr len,
* trigger after the current instruction.
*/
qemu_mutex_lock_iothread();
- cpu_interrupt(cpu, CPU_INTERRUPT_DEBUG);
+ if ((cpu->singlestep_enabled & SSTEP_NOIRQ) == 0) {
+ cpu_interrupt(cpu, CPU_INTERRUPT_DEBUG);
+ }
qemu_mutex_unlock_iothread();
return;
}
```
|